1. Field of the Invention
The invention relates to an improved process for the manufacture of an olefin polymer composition where corrosive trace cocatalyst and/or catalyst residues are removed from the hydrocarbon gas recycle stream prior to compression and re-use in the polymerization zone(s).
2. Description of the Prior Art
The general use of one or more reaction zones to manufacture a polymer composition is described in prior art and further advanced by U.S. Pat. No. 6,586,537, the disclosure of which is incorporated herein by reference in its entirety.
In the typical prior art polymerization process, a Zeigler-Natta type catalyst and cocatalyst are often added to one or more reaction zones to produce an olefin polymer composition which is typically withdrawn from the final reaction zone and transferred to one or more flash vessels where the product polymer composition is separated from a hydrocarbon gas stream that is predominantly comprised of a diluent and unreacted monomers. This hydrocarbon gas stream will typically contain trace amounts of cocatalyst (e.g. aluminum alkyls) and catalyst that remain with the vapor phase. This stream is typically compressed downstream so that it may be treated further in a recycle section so as to recover the monomer(s) and diluent for re-use in the reaction zone(s).
Prior art processes with a Zeigler-Natta type catalyst and an alkyl cocatalyst, e.g. triethylaluminum (TEAL) typically suffer decreased reliability in the downstream rotating machinery as the residual co-catalyst and catalyst residues are known to aggressively deteriorate rotating machinery, particularly most compressor, packing materials.
While it is known that a mixture of a long-chain carboxylic acid and hydrocarbon inert scrubbing liquid can be used to remove residual alkyls from a gas stream (as disclosed in U.S. Pat. No. 4,826,665, the disclosure of which is incorporated herein by reference), there is no process disclosed in the prior art to remove trace alkyls or catalyst residues in a continuous manner from polymerization processes and the optimal carboxylic acid and oil mixture is not specified.
The present invention provides an optimized process which can be used for the manufacture of an olefin polymer composition that overcomes the drawbacks of the prior art.